The compounds of formula IV, wherein R.sup.1 is as defined under (a) above, are known from U.S. Pat. Nos. 4,443,448 and 4,525,360 and are themselves valuable intermediates for the preparation of pharmacologically active indanes and indenes known from the aforesaid U.S. patents.
The novel indenes of Formula I make it also possible to prepare the intermediates IV in excellent yield and with a variation in the substituent R.sup.1 of a much wider scope than the method described in the abovementioned U.S. Patents.